1. Field of the Invention
This invention relates generally to powered, motorized riding trowels for finishing concrete surfaces. More particularly, our invention relates to protective edge guards for motorized riding trowels classified in United States Patent Class 404, Subclass 112.
2. Description of the Prior Art
Large, self-propelled riding trowels have become widely accepted in the concrete finishing arts, where they are particularly effective for rapidly and efficiently finishing large areas of plastic concrete. Modern, high-power, multiple engine riding trowels with power steering are highly desirable. They can finish large surface areas of wet concrete much more efficiently than single engine riding trowels or the older xe2x80x9cwalk behindxe2x80x9d trowels. Significant savings are experienced by the contractor using such equipment with large jobs, as time constraints and labor expenses are reduced.
Typical riding trowels have two or three downwardly projecting rotors that contact the concrete surface and support the trowel weight. Each rotor comprises radially, spaced apart finishing blades that frictionally revolve upon concrete surface. The rotor blades can receive circular finishing pans for treating green concrete. When the rotors are tilted, steering and propulsion forces are frictionally developed by the blades (or pans) against the concrete surface. Riding trowels finish large surface areas of wet concrete more efficiently than older xe2x80x9cwalk behindxe2x80x9d trowels. Significant savings are experienced by the contractor using such equipment, as time constraints and labor expenses are reduced.
Holz, in U.S. Pat. No. 4,046,484 shows a pioneer, twin rotor, self-propelled riding trowel wherein the rotors are tilted to generate steering forces. U.S. Pat. No. 3,936,212, also issued to Holz, shows a three rotor riding trowel powered by a single motor. Although the designs depicted in the latter two Holz patents were pioneers in the riding trowel arts, the devices were difficult to steer and control.
Prior U.S. Pat. No. 5,108,220 owned by Allen Engineering Corporation, the same assignee as in this case, relates to an improved, fast steering system for riding trowels. Its steering system enhances riding trowel maneuverability and control. The latter fast steering riding trowel is also the subject of U.S. Des. Pat. No. 323,510 owned by Allen Engineering Corporation.
U.S. Pat. No. 5,613,801, issued Mar. 25, 1997 to Allen Engineering Corporation discloses a power-riding trowel equipped with separate motors for each rotor. Steering is accomplished with structure similar to that depicted in U.S. Pat. No. 5,108,220 previously discussed.
Allen Engineering Corporation U.S. Pat. No. 5,480,258 discloses a multiple engine riding trowel. The twin rotor design depicted therein associates a separate engine with each rotor. As the engines are disposed directly over each revolving rotor assembly, horsepower is more efficiently transferred to the revolving blades. Besides resulting in a faster and more efficient trowel, the design is easier to steer. Again, manually activated steering linkages are used. Allen Engineering Corporation U.S. Pat. No. 5,685,667 discloses a twin engine riding trowel using xe2x80x9ccontra rotation.xe2x80x9d
Modern riding trowels, such as the Allen trowels with multiple motors listed above, are characterized by relatively high power. Simply stated, large, powerful riding trowels finish large work areas faster. Although earlier riding trowels used manually-operated levers for steering, modem high-power trowels are easier to control with power steering. For example, Allen Engineering Corporation, the owner of this invention, has developed high power, hydraulically controlled trowels illustrated in U.S. Pat. Nos. 6,106,193, 6,089,787, 6,089,786, 6,053,660, 6,048,130, and 5,890,833. It is now well recognized that power steering systems engender the maximum overall performance. Quick and responsive handling characteristics optimize trowel efficiency, while contributing to operator safety and comfort. All of these factors translate to vital speed at the job site.
As a practical matter it can be difficult to properly finish concrete regions immediately adjacent walls or other obstacles with motorized finishing trowels. There is an annular gap between the outermost radial edges of the rotor blades and the periphery of the conventional blade guard that concentrically shrouds them. Even if, for example, a conventional riding trowel is driven into gentle contact with a surrounding wall at the extreme edges of a job site, there will still be an inaccessible boundary region that is out of reach of the rotor blades that remains unfinished. Further, trowel contact with the surrounding wall or other obstacles within the work space can result in damage, both to the trowel and/or the items or structures forcibly bumped by the trowel. As trowel speed is increased, the frequency of unwanted collisions inevitably increases. Conventional trowel guards that shroud the rotor can scrape against and possibly mar or damage the wall or other structures impacted. Accordingly Allen has developed a rotating ring system for minimizing impact damage in walk-behind trowels, as illustrated in U.S. Pat. No. 6,019,545.
U.S. Pat. Nos. 5,221,156 and 5,533,830 disclose concrete finishing machines comprising a rotatable, disk-shaped guard that is spaced above the revolving finishing blades. The coaxially aligned guard disk contacts adjacent walls and obstacles, and provides a limited guard function. In these machines the guard disk centers are coaxially coupled to downwardly-projecting drive shaft structure at the center of motor rotation. For clearance purposes, rotor guards secured according to the teachings of the latter patents must be relatively flat and disk-like, and they are not adequate for riding trowel use.
The preferred trowel comprises a two or more spaced apart rotors gimbaled to the frame. Each downwardly projecting rotor revolves multiple, radially spaced apart blades that frictionally contact the concrete. One or more internal combustion motors power the rotors, either through mechanical gear boxes or hydraulic means. If hydraulic actuators are used, suitable hydraulic pumps for energizing the hydraulic accessories are mounted upon the trowel frame and driven by the motors. Where power steering is employed, suitable joysticks are conveniently placed near the operator.
The preferred edge guard system comprises a supporting frame portion that structurally mounts upon each rotor, circumscribing the center of rotation. Tilting movements of the rotor responsible for steering thus deflect the guard system as well. The guard frame suspends a plurality of rollers at radially spaced apart intervals. The guard ring comprises an inner, upper lop coaxially connected to a larger, lower, outer loop that is exposed to obstacle contact. Radially spaced apart spokes extending between the inner and outer loops reinforce the rotating ring. Each roller comprises spaced-apart upper and lower flanges disposed on opposite sides of a roller surface, between which the inner loop of the guard ring is captivated.
When the trowel inadvertently contacts an obstacle, the lower guard ring makes first contact. Rather than marring or scratching an impacted surface, the guard ring is rotatably deflected, enabling the power trowel to smoothly traverse boundary regions of concrete surfaces. Impact forces from inadvertent collisions are dissipated as the guard ring rotates and the trowel is non-destructively deflected.
Thus a basic object of our invention is to provide a power rising trowel especially adapted to minimize collision damages.
Another fundamental and basic object is to provide a riding trowel with a guard system that minimizes the marring or defacement of impacted items.
Another object is to provide a trowel of the character described that reaches and finishes border regions near walls and obstacles.
Another fundamental object is to provide a guard system of the character described that does not interfere with the normal steering function and tilting characteristics of power riding trowel rotors.
A similar object is to provide a high power riding trowel that may be driven closely up against walls and other obstacles during concrete finishing.
Another object of our invention is to provide a high power riding trowel of the character described that remains safe and stable despite impact with nearby walls and obstacles.
Yet another object is to provide a highly stable riding trowel guard system that concentrically moves with the rotor.
Another important object is to provide an impact-responsive guard system for power riding trowels that protectively shrouds the blades.
A related design object is to provide an impact-accommodating guard system that may be employed upon a variety of modem high powered riding trowels, including hydraulically-steered trowels, hydraulically driven trowels, and trowels with two, three or more rotors.
Still another object is to provide a riding trowel guard system that accommodates reasonable impact forces in response to collisions.
Another object is to provide an impact-accommodating guard system of the character described for riding trowels driven by diesel or gasoline powered motors.
It is also an object to provide a guard system of the character described that may be retrofitted to hydraulically steered and hydraulically driven designs.
A related object is to provide a guard system for multiple rotor riding trowels that tends to isolate each rotor from shocks experienced from collisions.
Another basic object is to provide a guard system for riding trowels that works with either standard rotation or contra rotation.
A further object is to provide a trowel guard system that is readily compatible with conventional blades, combo-blades, or finishing pans.
These and other objects and advantages of the present invention, along with features of novelty appurtenant thereto, will appear or become apparent in the course of the following descriptive sections.